Design, Synthesis, And Biological Evaluation Of Novel Multi-targeted Inhibitors To Treat Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an intractable autoimmune disease, affecting multiple joints of RA patients. RA patients account for 1% of the general population and the main therapy of RA relies on the drugs. There are three main categories of drugs, e.g., non-steroidal anti-inflammatory drugs, disease modifying anti-rheumatic drugs and glucocorticoids, to relieve this disease. Progress in the understanding of the RA pathology led to the development of new biological agents, e.g., anti-TNF agents, IL-1 receptor antagonists, B cell monoclonal antibodies and T cell co-stimulation modulators. Biologics are highly selective and efficacious, however, these protein therapeutics are administered intravenously or subcutaneously due to their large dalton. Besides, they have the potential to induce immunogenicity as foreign protein. In addition, biologics need special transport and storage conditions, so their cost of acquisition is high. As a result these biologicals are limited to clinical use on a large scale. Spleen tyrosine kinase is identified as a potential target to treat RA. The development of novel Syk inhibitors has been carried out in our group. Inspired by the structure of thiazolopyrimidine diamines designed by Roche Inc., two categories containing 40 compounds, cyclopentapyrimidine diamines (1, A01-A21) and dihydrofuropyrimidine diamines (B01-B18), were synthesized. During the kinase assay test, we found several compounds also exhibited potency against platelet-derived growth factor receptor a (PDGFR-a) and c-Kit, which played great improtance in the pathogenesis of the RA disease. All the compounds were evaluated through Syk assay test, while some of them were also undergone another two assay tests against PDGFR-a and c-Kit. As for the Syk assay, one compound showed good inhibitory activity (IC50< 10 μM) and 11 compounds showed moderate potency (10 μM< IC50< 25 μM). Three compounds owned both PDGFR-a and Syk inhibitory activity. Four compounds exhibited c-Kit and Syk inhibitory potency. Totally, compounds, B06 and B11, targeted three kinases were discovered. Based on the results of Syk assay, the structure-activity relationship was summarized for the guidance of further structural optimization. Ultimately, several compounds were selected to assess their cellular potency. B11 possessed great anti-proliferation activities on fibroblast-like synoviocytes (IC50:3.21 μM) and mast cells (IC50:2.03 μM) in vitro. In the meantime, the compound significantly decreased the secretion of excreted factors of the corresponding cells, showing great anti-RA efficacy. In summary, a compound firstly targeted three kinases, Syk, PDGFR-a and c-Kit, was excavated with fine cellular activity and worth further development.